Yarn package

ABSTRACT

A yarn package comprising freshly drawn polyamide yarn in which the yarn on withdrawal possesses substantially constant shrinkage tension throughout its wound length by arranging for the yarn to be wound onto the package at different balloon (wind-on) tensions.

United States Patent 72] Inventors Christopher John Rollason Pontypool;Gerald Henry Sutclilt Tinsley, Doncaster,

- England [21] AppLNo. 775,511

[22] Filed Nov. I3, 1968 [45] Patented Jan. 5, 1971 [73] AssigneeImperial Chemical Industries Limited London, England a corporation ofGreat Britain [32] Priority Nov. 17, 1967 I3 3] Great Britain [54] YARNPACKAGE 2 Claims, No Drawings [52] U.S.Cl. 242/159, 57/156 [51] lnt.ClB6Sh 55/00; DOlh l/26 [50] Field olSearch 57/106T. 94, 93, 92, 96, 156;242/18, 18T, 26.1, 46.2. 45, 147, 159

[56] References Cited UNITED STATES PATENTS 1,965,163 7/1934 Truslow Y5'7/93 1,985,851 12/1934 Brooks et a1. 57/94 3,315,904 4/1967 Hardee242/18 3,329,360 7/1967 Schippers.. 242/45X 3,357,655 12/1967 lwnicki etal. 57/94X 3,450,371 6/1969 Phillips 57/93X Primary ExaminerDonald E.Watkins Attorney-Cushman, Darby & Cushman ABSTRACT: A yarn packagecomprising freshly drawn polyamide yarn in which the yarn on withdrawalpossesses substantially constant shrinkage tension throughout its woundlength by arranging for the yarn to be wound onto the package atdifferent balloon (wind-0n) tensions.

1 YARN PACKAGE The present invention relates to thermoplastic polyamidefilaments, yarns and the like. More particularly, the invention relatesto an improvement in the properties of such structures.

For the sake of convenience that expression yarn will be usedhereinafter to describe single and multifilament continuous strands.

When a process or treatment is to be either continuously or batchwiseapplied to a yam so as to modify or otherwise alter the properties orcharacteristics of that yarn, it is often particularly important thatsuch a process or treatment be applied uniformly, thus ensuring aconstancy of new yarn properties from one portion or section of the yarnto another.

Unfortunately, such a consideration frequently suffers from the seriouslimitation that however meticulous the technical attention given to theprocess or 'treatmentinquestion, its resultant effect can be no betterthan that which the chemical and physical uniformity of the yarnpermits,which in turn will depend, iutcr alia, upon those processes andtreatments which the yarn may have already undergone.

In any yarn process ortreatment, therefore, the ultimate desired resultwill depend in the first instance upon the constancy, uniformity andlevelness of the properties and character of the yarn prior to thatprocess or treatment. In other words, the success of each processingstep will depend, inter alia, upon those preceding it.

Before a polyamide yarn is woven, knitted or otherwise made up into afabric or other structure it may undergo a succession of operations thatmay at the same time undesirably influence its properties. i

In particular, a molecularly oriented or drawn polyamide yarn, after ithas been wound onto a bobbin or like container following drawing, isfrequently found to possess varying properties along its length onunwinding which are sufficient to adversely influence the behavior ofthe yam both chemically and physically when it is subjected to furthertreatments, often to such an extent that in some instances'the final useto which the yarn is put may be significantly affected.

Very often such variation in yar'n properties may be attributed to thevariable extent of lengthwise shrinkage of yarn that arises throughoutthe yarn package during and after its formation following the drawingprocess,which in turn may be ascribed to the manner in which such apackage is built.

The extent of polyamide yarn shrinkage usually changes graduallythroughout a wound package, i.e. from the inside or core of the packagetothe outside, or vice versa, and although in some instances the gradualvariation in yarn character which results may be insufficient to lead'tovisible defects or other detrimental changes in yarn taken from a singlepackage, there is, regardless of the manner in which yarn properties mayvary across the diameterof a package, usually a substantial differencebetween the character of the yarn on the inside of the package and thatin the outer layers of the package. Under these circumstances, the jump"in properties when the transfer-tail of one package is joined to theleading end of another as in magazine creelirig is sufficient to cause asignificant imperfection in a product derived from such joined yarns. I

In particular, when drawn polyamide yarn is wound onto a bobbin the yarnis still tending to shrink after drawing. The innermost package layersare held firmly against the container barrel and are unable to shrinkany further, while the outer package layers are able to shrink to someextent onto the layers beneath. The middle package layers are less freeto shrink but are also subjected to crushing due to shrinkage of theouter layers. Thus, when yarn is taken from the package, the residualtendency to shrink is lowest in yarn from the middle of the package andgreatest in yarn from the inside.

In the case of a 3-pound polyamide yarn package, the lowest shrinkagetension values occur in yarn taken from approximately the l to 2 poundregion of'the package.

Thus, it is an object of the present-invention to provide a package ofpolyamide yarn that'is substantially free from such variation ofshrinkage tension on unwinding as is likely to lead to an unsatisfactoryfinal product.

it is a further object of the presentinvention to provide a processwhereby the aforementioned object may be successfully achieved. I

Accordingly, the present invention provides a yarn package comprisingfreshly drawn polyamide yarn in which the yarn on withdrawal possessessubstantially constant shrinkage tension throughout its wound length.

In the context of this invention the'expression substantially constantshrinkage tension meansa variation about a mean of not more than 10percent. i

The invention further provides a process for building a package of drawnpolyamide yarn in which the yarn on withdrawal possesses substantiallyconstant shrinkage tension throughout its wound length, by arranging foryarn to be wound onto the package at different balloon (wind-on)tensions so as to counteract the forces which develop in the packageafter it has been built.

Preferably, the necessary changes in balloon tension are brought aboutby arranging for an appropriate change in the speed of the spindledriving the package.

Generally, such a program consists of commencing to build a package ofdrawn yarn at a low balloon tension (without deteriorating drawingperformance), increasing to a maximum at some specific package weight,and thenfinally decreasing to a low balloon tension. Such variation inballoon tension may be achieved by-arranging for an initial continuousincrease in the speed of the spindle driving the package followed by acontinuous decrease in the spindle speed.

This program, which is applicable to packages wound in' parallel layers,e.g. the so called long to short packages, winds yarn onto the packageat a sequence of balloon tensions that are designed to counteract theinternal forces which develop in a package after it has been built andwhich are caused by the differential shrinkage of yarn within thepackage.

in order to achieve the minimum variation in shrinkage tensionthroughout the full package, it has'been found desirable to continuouslyincrease the balloon tension until about one third of the full packagehas been built.

When yarn is subsequently taken from the package it ex-- hibits asubstantially constant shrinkage tension of the lowest level.

Thus, the effect of differential shrinkage of drawn polyamide yarnwithin a package which may give rise to tension fluctuations in therunning yarn during subsequent treatments, such as false-twist bulking,with commensurate stripiness and variation in dye uptake in a resultingfabric, may be met by an appropriate variation in the speed of thespindle driving that package. 7

Normally, programming will be applied by a suitable profiled cam whichwill cause the spindle to be rotated at an appropriately varyingrotational "speed during the winding of the full package. Equipment forprogramming spindle speeds is available from a number of sources and isreadily accessible to those familiar with the art. A

By shrinkage tension is meant, that tension which occurs -when thepolyamide yarn is held to substantially constant length and heated to atemperature of li5 C. Alternatively, a closer simulation of tensionsdeveloped during false-twist bulking processes can be achievedbymeasuring the tension required to stretch the polyamide yarn'by 3percent while passing it over a heater plate at a yarn temperature ofl90i5C.

The effect of shrinkage tension is important in any process in whichpolyamide yarn is relaxed by heat or steam and where uniformity ofproperties and character is important. Thus, e.g., in finishing fabricscomprising in part'or in whole polyamide yarns, heat-setting is likely.to be far more effective if the fabric comprises polyamide yarnsprepared according to the present invention. y

The invention is applicable to any polyamide yarn that has a tendency toshrink after being held under tension, especially after drawing, and inparticular there may be mentioned polyamide (which expression is to betaken as including copolyamide) yarns such as those derived frompolyhexamethylene adipamide, polyhexamethylene sebacamide andpolyepsilon caprolactam.

In the following illustrative examples, there are particularly describedprocesses whereby the beneficial effects of the present invention may berealized.

In the examples a 70 denier, 34 filament polyhexamethylene adipamideyarn was drawn at 3,300 feet/minute before it was wound-up using a ringand traveller system to form a 3 pound package, the yarn being wound onthe package in parallel layers of decreasing traverse length.

Example 1 In conventional prior art systems, the spindle speed mightwell be adjusted to give a constant balloon tension of about 3 gramsthroughout the package build. Under the characteristics of the presentsystem this was achieved with an initial spindle speed of the order of9,600 r.p.m. decreasing to about 6,800 rpm. by the time the package wascomplete. I

After unwinding the package about two weeks later, the shrinkage tensioni.e., the tension required .to stretch the yarn by 3 percent whilepassing it over a heater plate at a yarn temperature of 1905C. variedfrom 32 grams to 48 grams, with the lowest level being at aboutone-third of the full package and the highest at the barrel of thecontainer.

Woven and weft knitted fabrics prepared from yarns subsequently bulkedby false-twisting. and dyed in the usual manner clearly showed avariation in dye-uptake.

EXAMPLE 2 In the process of the present invention, the spindle speed wasprogrammed to give balloon tensions starting at about I gram, increasingto about 8 grams at approximately one-third of the full package and thendecreasing to about l'grarh again at the full package. In this caseinitial spindle speed was of the order of 8,500 r.p.m. increasing toapproximately 9,200 r.p.m. and then decreasing to about 5,700 r'.p.m.

After unwinding the package about two weeks later, the shrinkage tensionvaried only between4'0 and 45 grams and the dyeing differences inbulkedyarn fabrics were greatly. reduced with the largest differencesbeingb'eing barely visible.

We claim: I 1

l. A process for winding a package of freshly drawn polyamide yarn on abobbin with a ring-and-traveller system in order that the yarn onunwinding possesses substantially constant shrinkage tension along itswound length, being the'tension required to stretch the yarn by 3percent while passing ,it over a heater plate at a yarn temperature of'190i-5C., by programming the speed of the spindle carryingthe bobbin togive a gradually increasing yarn balloon tension until approximate,-

ly one-third of the full package has been-wound, and then a graduallyreducing yarn balloon tension over the remainder of the winding period.

2. A yarn package of freshly drawn. polyamide yarn when wound accordingto the process as claimed in claim I.

2. A yarn package of freshly drawn polyamide yarn when wound accordingto the process as claimed in claim 1.